The broad objective of this research plan is to examine the control of several organ-specific functions in established clonal strains of differential mammalian cells in culture. The studies will focus on hormone-producing pituitary cell strains and on cultures derived from the hypophysiotropic area of the hypothalamus. The methods to be used include immunologic, biochemical, cytologic, electrophysiologic and genetic techniques as they are applied to protein, peptide and amine synthesis and release by dispersed cell cultures. Particular emphasis will be placed on the mechanism of action of thyrotropin-releasing hormone (TRH), a tripeptide that stimulates both the release and biosynthesis of prolactin. The role of membrane receptors for TRH in mediating the actions of the peptide will be examined as will the role of TRH in controlling the number of its own receptors on the target cells. The pituitary cell culture system will be used as a model for electrophysiologic studies of protein-secreting nonexcitable cells. Using microelectrode techniques, we shall define the resting membrane potential and membrane resistance of the cells, the effects of secretagogues on membrane properties, and the role of ions and ion fluxes in the maintenance of membrane potential and protein secretion. Lastly, the pituitary cell cultures will be used as assay cells to monitor the establishment of hypothalamic cell lines that produce factors that control the functions of the anterior pituitary gland. The experiments proposed take advantage of several unique properties of tumor cells in culture, and permit studies that would be difficult or impossible to perform otherwise. BIBLIOGRAPHIC REFERENCES: Tashjian, A. H., Jr., Richardson, U. I., Strunk, R. C. and Ofner, P., Differentiated functions in clonal strains of hepatoma cells, In: Gene Expression and Carcinogenesis in Cultured Liver, Academic Press, N. Y., 1975, pp. 168-180. Strunk, R. C., Tashjian, A. H., Jr. and Colten, H. R., Complement biosynthesis in vitro by rat hepatoma cell strains, J. Immunology 114:331-335, 1975.